BAY BUILD-UP: Accumulated sediment in Newport Harbor can cause boats to run aground or, as shown in this photo, be lifted from the water at low tide. Elected leaders will consider a multimillion-dollar effort to dredge the bay, in hopes of at least getting matching funds from the federal government, which is responsible for harbor maintenance.

NEWPORT BEACH – Thousands of boaters would enjoy relief from an increasingly shallow harbor under a multimillion-dollar dredging plan to be unveiled today.

Silt and sediment ferried by urban runoff have gradually accumulated in the bay over the years, causing boats to run aground at low tide.

Elected leaders today will discuss investing $2 million to $4 million over the next several years to clean up the most problematic areas of the harbor, said Dave Kiff, assistant city manager.

The 800-acre bay has had piecemeal dredging from time to time, but hasn’t been comprehensively dredged since its dedication in 1936.

Maintenance of the bay is a federal responsibility, but the recreational harbor is a low priority compared with commercial ports.

Rep. John Campbell, R-Newport Beach, earlier this year announced plans for legislation that would transfer future responsibility for maintaining the bay to the city in exchange for federal funding of a thorough dredging project.

That effort is estimated to cost about $12 million, an amount federal officials are hesitant to cover even though doing so would absolve them of future costs.

“They look at it like, ‘Well, we haven’t spent anything (in the past), so how does that save us money?'” Kiff said.

Local leaders say they haven’t given up on getting help from Washington and that chipping in city cash might help forge a compromise.

“We don’t want to foreclose on the opportunity for federal funding, but there may be an appropriate local cost-share that will sort of be able to kick-start the project,” said Councilwoman Leslie Daigle.

Assuming the City Council approves funding, significant planning and study would be needed before dredging could commence. It’s not yet clear how much benefit a few million dollars can provide the roughly 10,000 boats in Newport Harbor.

One question mark is how to approach the project – should the city seek to modestly improve a significant portion of the bay, or should it fully dredge a smaller area?

Another hurdle involves pollution. The harbor muck in some spots is contaminated with small amounts of mercury or toxins related to pesticides.

That sediment would normally be dumped offshore after being scooped out, but if it’s contaminated, it might have to be trucked to a landfill. That requirement could triple or quadruple the sediment disposal costs, Kiff said.

Despite its multimillion-dollar price tag, dredging is just one part of keeping the bay navigable. Officials estimate that more than $100 million has been spent over the years preventing sediment from leaving watershed areas such as Tustin and Irvine and making its way to Upper Newport Bay and Newport Harbor.

The Newport Beach City Council will discuss the dredging issue during a study session at 3:30 p.m. today at 3300 Newport Blvd.